[hpsdr] PennyWhistle Comments

[Graham / KE9H]

Dick:

Comments embedded below.

--- Graham / KE9H


Dick Faust K9IVB wrote:
 >
 > I have some comments and questions that are not critical, but
 > thought that this was a good time to bring them up.
 >
 > I noticed that Communications Concepts had output cores and
 > transformers of a similar size to the BN-43-3312 in 43
 > material.
 >
 > These cores and transformers have the tubes and end plates
 > already attached.  I have attached a file that has comparison
 > of mechanical features.  The RF800-0 is just the core [$4.85]
 > and the RF800-4 is 4:1 [$5.25], other sizes are available but
 > this is the closest size.
 >
 > I wonder if either of these would be a good alternative to
 > the BN-43-3312 .  I do not know what materials are used in
 > the RF800-4 windings, but probably not the #30 wire wrap wire
 > construction that PennyWhistle currently uses.

The PennyWhistle Alpha-1 layout will accept the C.C. cores,
up to an inch in length.  I'll see if the minimum inductance is
acceptable.

As far as secondary windings, you want two turns of wire, with
the lowest resistance and largest amount of surface area, that
you can get through the holes. (I used paralleled, silver
plated wire wrap wire.)

Since the holes on the C.C. transformers are bigger, two turns
of silverplated #16 or whatever fits would be great.
RF Parts sells silverplated copper wire, and teflon insulation
to slip on it for just such PA windings.

Regular copper works too, but with slightly more loss at
the higher frequencies.  You won't see any difference below
20 MHz.

 >
 > Any one have comments / thoughts about this?
 >
 > I have several PC-CPU heat sinks that have been pulled from
 > non working motherboards.  The nice copper ones from older
 > Pentium units are just a little too short to fit the spacings
 > on the board.  I have 2 others from a Pentium 4 and an AMD
 > Athelon made by TiaSol that are about 3 1/4 " long and 2 5/8"
 > wide [~83mm x ~69mm].  It appears similar units are available
 > at FRY's & others for reasonable prices note the Socket
 > identificatioon as most vendors list by socket type
 >
 >
 > http://www.taisol.com/CEP420151D.html
 > CEP420151D from TaiSol Pentium 4  - Socket 478
 > This one needs a different method of attaching the fan &
 > appears to have a lot  of surface area - nice flat area on
 > bottom with a reasonably thick platform to drill and tap
 > may not need a fan for intermittent duty.
 >
 >
 > http://www.taisol.com/pdf/AMD_Solution.pdf
 > CEK806 from Taisol AMD   [not exact picture of my heatsink
 > but very close]
 >
 > I plan to start with the one like this. Can mount the entire
 > PennyWhistle assembly vertical by the fan.
 >
 >
 >
 > http://www.taisol.com/cgk742092_intel.html
 > CGK742__2  Intel 370 and AMD 462 Athlon Sockets  [another
 > possibility as fan is attached]
 >
 >
 > <http://www.tai-sol.com//pdf/cgk742002.pdf>
 >

You have several interesting, compact cooling approaches.  I personally
like large silent finned heatsinks, but the packaging problems
are bigger.

 >
 > Yesterday I noticed the Pennywhistle site on HPSDR and
 > thought that this was a good thing.
 >
 > At any rate I think, when you are ready, there should be some
 > sort of announcement to the Softrock group and the FT817
 > group on Yahoo.  With 5621 and 9873 members respectively they
 > could generate a substantial volume to drive down the cost of
 > the kit and there is usually always  someone looking for a
 > little more power.  The PicaStar group might also be
 > interested even though the Yahoo site closed this year.

Picastar needs another preamp stage, hence the G6ALU design.

Softrock would work with this design if the control voltage
was inverted.  Rob Brown, M0RZF, is working on a similar amp
integrated with an LPF bank on a single board.

 >
 > I do not know if you plan another pass on the PCB.  

There is always a reason to do another pass of the PCB. :-)

 > If you do
 > the input attenuator with SMD parts is severly limited, might
 > wish to eliminate or allow for 1/2 W metal oxide axial
 > resistors.  

 > The SMA jacks are nice [but costly in a system] -
 > could use direct coax hookup connection or 2 pin like power
 > connector.

The footprint of an SMA connector is almost ideal for directly
soldering a coax to a PC board. Use the center hole, and solder the
shield through one of the ground holes.  The question is
whether people want BNC instead of SMA, which is a different
footprint.

 >
 > How is the harmonic output of the amp?  I know that G6ALU
 > indicated clean output for his amp, but this one is a little
 > different.  I do not have a spectrum analyzer but considered
 > some LP filters from Kits and Parts or the HFproject group.

This amp, Rob Brown's Softrock amplifier, and the G6ALU
all require an LPF to follow the amp for harmonic supression,
to be legal.

For HPSDR, the ALEX (Alexaires) filter pack includes transmit
LPFs for each band, up to 100 Watts peak power, and should
integrate nicely with the hardware and software.

Of course, you can always use something else.

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